The $\mathrm{Si}-\mathrm{Si}$ bond length in silicon is $235\mathrm{pm}$ and the $\mathrm{Cl}-\mathrm{Cl}$ bond length in chlorine is $199\mathrm{pm}$. The simple additive covalent radii predict an $\mathrm{Si}-\mathrm{Cl}$ bond length of 217.0$\mathrm{pm}$, yet the measured value in $\mathrm{SiCl}{}_4$ is $202\mathrm{pm}$. The best interpretation is:

1. Athe additive value should be the sum of the two bond lengths, $434\mathrm{pm}$, so the measured value is far too small
2. Bthe measured bond is shorter than the additive value because the electronegativity difference gives the bond polar (partly ionic) character
3. Cthe measured bond is longer because covalent radii are not additive for any bond
4. Dthe measured bond is shorter because silicon has lost all its valence electrons in $\mathrm{SiCl}{}_4$